A study that suggested common moisturizers may increase the rate of tumor formation in mice with a high skin cancer risk has provoked a storm within the industry. The research appears in this month’s Journal of Investigative Dermatology, along with some fierce criticisms from the manufacturers of the creams.

Original study

Run by scientists at Rutgers State University of New Jersey, the study concluded that applying a number of commercially available moisturising creams (Dermabase, Dermovan, Eucerin or Vanicream) to the skin of mice pre-treated with UVB (to make them high risk for skin cancer) increased the rate of tumor formation.

Led by Dr Yao-Ping Lu, the team radiated populations of approximately 30 mice with UVB (30mJcm-2) twice a week for 20 weeks in order to predispose them to tumor formation. After the end of the radiation period the mice were treated with 100mg of the creams, once daily, 5 days a week for 17 weeks.

The formation and size of tumors were measured throughout the study period before histological characterization of the mouse skin was performed at week 18. Although at the end of the study the number of mice with tumors was not statistically different in the treated groups in comparison to the control groups, there was a significant increase in both the rate of tumor formation and the total number of tumours.

Dodgy statistics?

However, scientists from Beiersdorf and Pharmaceutical Specialties, manufacturers of Eucerin and Vanicream respectively, have responded with a number of complaints focusing on the study design, the statistical treatment of results and the relevance of the findings for humans.

Franz Staeb and fellow researchers from Beiersdorf picked apart the statistical analysis of the data, claiming the sample size of 30 mice was not big enough to make relevant conclusions. “Taken together, we have serious doubts about the validity of the statistical analysis and relevance of the conclusion drawn from the results,” wrote the Beiersdorf scientists.

For Ralph Ellefson, a consultant at Pharmaceutical Specialties, the main gripe was the allusions to human relevance that he felt the original authors had made. He took issue with suggestions that the model using UVB-pretreated high risk mice resembled humans who had undergone UV exposure early in life.

Study could damage manufacturers’ reputation

According to Ellefson these suggestions have “inflicted unjustifiable damage to the reputations of the tested moisturizers, according to many commentaries in the lay press and correspondence to the manufacturers”. However, Lu and the team point out that their original article is conservative about the relevance of the work to humans and they cannot be held responsible for the interpretations of their work by others. A number of other industry experts have also commented on the study with some agreeing that further tests are necessary in order to investigate the human relevance of the work.

Brian Diffey, emeritus professor of photobiology at Newcastle University, agrees that the UVB-pretreatment of the mice is a poor surrogate for human sun exposure. However, he states that further work is needed to evaluate the risk, as opposed to the hazard, of the creams to humans. But, Professor Jonathan Rees from the University of Edinburgh warns that mice and humans are not very similar when it comes to skin cancer and questions the clinical relevance of the study.